If RED can connect XG behind firewall?

Question

Dear All, Our customer was interesting with Sophos RED. But they have their old firewall and cannot be replaced with XG... So XG can only be placed on LAN, and mapping a public IP for it. XG sets the default static route to old firewall for out. (XG only has one LAN interface, and no other interface.) 
 I am not sure if RED can connect the XG behind old firewall? Because XG doesn't have a WAN interface for RED to connect. 
 Anybody knows if this can work? 
 Thanks~

lferrara · Accepted Answer

Shunze, 
 Thanks for the diagram. It helps a lot. Anyway your configuration can work. You have to make sure that proper ports are allowed through the firewall and and configure dnat on old firewall for necessary ports. Red uses different ports. Use the following kb: 
 
 Regards